This invention relates to electro-mechanical actuators, and more particularly, electro-mechanical actuators which release their loads in the event of an internal actuator failure or jam, and maintain their loads in the event of an external overload or jam. A jam refers to any failure causing an excess torque to occur in the actuator mechanism, whether the failure is internal or external to the actuator.
Prior art fail-free actuators for use in various critical applications including movement of aircraft control surfaces are constructed so that internal failure in the actuator itself does not prevent a separate backup actuator from governing the same load. Prior art fail-free actuators experiencing internal jams release their loads, failing-free, so that they do not cause an external overload on a backup actuator connected to the same load. However, many prior art fail-free actuators also release their external load in response to external overload situations, which may be an undesirable characteristic for some applications. In addition, many prior art fail-free actuators incorporate quick release mechanisms that are not easily reassembled or reversed after a quick release occurs. For example, some prior art quick release mechanisms use movable pins and rollers to couple the actuator output member to the actuator drive system. In response to a jam, the pins and rollers move into positions that require actuator maintenance to reset the quick release mechanism in order to restore functionality to the actuator. As a result, testing of the "fail-free mode" in prior art actuators is difficult.
In view of the foregoing, it is an object of this invention to improve and simplify rotary output and linear output, fail-free, electro-mechanical actuators.
It is a further object of this invention to enable simplified testing of a fail-free actuator by incorporating a reversible quick release mechanism.